The invention relates to a gas generator comprising at least two combustion chambers.
In such gas generators, which may be designed as multiple-stage gas generators, one or more propellant charges are ignited, in order to be able to generate different quantities of gas. If not all of the propellant charges are to be ignited, a so-called ignition transfer must be prevented. The igniting of a propellant charge must not in fact lead to an auto-ignition of the other propellant charge, for example by generated hot gas flowing into the combustion chamber of the propellant charge which is not to be activated. So that this is ruled out, the outflow openings in the combustion chambers are usually closed by membranes, preferably metal foils. The metal foils are constructed such that they are only destroyed by the associated propellant charge, but withstand a destruction owing to the flow of gas and particles on igniting of another propellant charge. At the same time, the membrane can also serve for the hermetic sealing of the combustion chamber, so that no humidity can penetrate into the combustion chamber. So that the generator remains capable of functioning over a period of years, it must be ensured that the membrane remains fastened to the combustion chamber wall. Also on igniting of a propellant charge, the membrane of a propellant charge which is not to be ignited must in no way detach itself from the combustion chamber in the region of its edge, otherwise a stream of gas would arrive into the combustion chamber and ignite the propellant charge.
The invention provides a gas generator in which an ignition transfer can be avoided even more reliably. This is achieved in a gas generator which comprises at least two combustion chambers filled with propellant charges and delimited by combustion chamber walls. The combustion chamber walls have outflow openings which in a non-activated state are closed by at least one applied membrane having an edge. One of an additional fastening device and a protective device is provided at least sections of the edge of the membrane. The device prevents a coming-off of the edge of the membrane from the combustion chamber wall. The additional fastening device or the protective device prevents the edge from coming off owing to the stresses which are produced by the gas stream of an ignited propellant charge.
Preferably the membrane is fastened on the side of the combustion chamber wall facing away from the propellant charge. In this embodiment the membrane is not provided in the combustion chamber but outside it, so that the edge of the foil is pressed against the wall by the pressure stress and flow stress on igniting a propellant charge which is not associated with the membrane, and is not peeled off from it.
The fastening or protective device is arranged on the outer side of the membrane, in order to protect the edge of the membrane from the gas stream.
According to one embodiment, the fastening device is an adhesive applied from outside to the edge of the membrane, for example a metal adhesive.
According to another development, a protective foil is fastened externally on the edge of the membrane, the fastening devices always having to extend beyond the edge of the membrane so that it is also actually protected.
The protective foil can be a ductile metal foil which can be easily adapted to the geometric characteristics.
If the membrane is likewise of metal, the protective foil can be fastened to the membrane by welding.
Another embodiment makes provision for constructing the protective device as a depression in the combustion chamber wall, into which depression the edge of the foil is pressed and which thereby can not be caught directly by the gas stream, because it lies in the depression which is protected from flow.
The protective device can, furthermore, also be a projection of the combustion chamber wall, which runs along the edge so as to adjoin the edge. Also in this development, the projection serves to not expose the edge directly to the gas stream. The projection serves as a flow deflector.
According to a further embodiment, the membrane is open in peripheral direction and has peripheral ends. The protective device consists in that the end wall is chamfered or rounded. This design, which is favorable to flow, protects the end wall of the membrane from the gas stream.